Gripper block for printing presses



INVENTDH Z6 EOEEQT KNOX Patented Sept.V 13, 1927.

UNITED STATES 1,642,151 PATENT OFFICE.

ROBERT P. KNOX, 0F OAKLAND, CALIFORNIA.

f GRIPPER'BLOCK FOR PRINTING PRESSES.

Application filed November 2, 1926. VSerial No. 145,752.

. My invention relates particularly to an apparatus to holdy a sheet of material on the platen of a printing or color press during the operation of printing.

The principal object of my invention is to rovide a gripping block to be used in comiiination with the gripping fingers of a printing press platen'to hold the material to be printed on in a stationary posit-ion during the printing opertaion.

A further object of the invention is to provide a gripper block-for a printing press platen that consists of a spring urged plunger on which the material to be printed upon is adapted to be frictionally retained.

In this specification and the annexed drawings, t-he'invention is illustrated. in the form considered to be the best, but it is to be understood that the invention is not limited to such form, because it may be embodied in other forms, and it is also to be understood that in and by the claims following the description, it is desired to cover the invention in whatsoever' form it may be embodied.

Other objects of the invention will be understood from the following detailed description having reference tothe accompanying drawings, in lwhich:

Fig. 1 is a fragmentary Cross section through a cylindrical platen, showing the spring-actuated gripper block secured to the platen, a sheet placed over the block and platen for printing and the gripper fingers out of contact with the sheet.

Fig. 2 is a section, similar to Fig. 1, showing the gripper fingers oscillated into contacting position with the sheet. f

Fig. 3 is an enlarged cross section of the gripper block and the spring-actuated member therein.

Fig. 4 is an enlarged, longitudinal section of a modified form of gripper block.

Fig. 5 is an enlarged end elevation of a still further modied form of gripper block mounte`d on a bracket to secure the block to a printing press platen.

Fig. 6 is a plan view of the gripper block.

In Figs. 1 and 2 my invention is illustrated as applied to a rotary platen 10 of the type employed in printing presses for the execution of multi-color and other types of prints, but it is understood that the invention, by such modification as necessitates only the exercise of mechanical skill,

may also bev applied to other types of platens, including those having a flat impreSSiOn surface upon which the tympan is fastened. The rotary platen of the type here illusytrated is provided with end flanges 11,y in

construction, by which the oscillation 0f the shaft is effected, is well known in the art and is not a part of this invention, illustration thereof is deemed unnecessary, and only the parts of the platen that have a direct bearing upon the operation of my device are therefore shown in the drawings and described hereinafter. For the better understanding of the invention it may not be amiss, however, to point out that the fingers ordinarily employed in the type of platen shown are made in sections, resiliently' held together, so that a considerable difficulty is experienced in adjusting such fingers properly and that it is almost impossible by the use of them to prevent the movement of the sheet 14 from its adjusted position against the customary stops, not shown, on the platen. I prefer, therefore, to employ fingers 13, each of which is made in one piece and is firmly and adjustably secured to the shaft 12 by a set-screw 15.

The platen has a shoulder 16, formed along one side of the recess 11', at the periphery of the platen, and in registration with the margin at which the sheet 14 is held to the tympan surface of the platen. In this recess I secure boxes 17 by any suitable means, such as set-screws (not shown) in the ends of the flanges or by wedging the boxes one against the other between the flanges. The arrangement is also such that each finger 13 approximates central contact with each gripper blade 17, as shown in dotand-dash lines in Fig. 4.

Each gripper block 17 is provided with an open top, and a plunger member 18 is slidably mounted in the box so as to reciprocate therein. Resilient means, such as coil springs 19 have their ends secured in recesses in the base of the block 17 and to hold the plunger extended above the top of the block 17. Rods 20 extend through the plunger in transverse openings 21, as shown in Fig. 3, or rods 22, extending longitudinally through the plunger in longitudinal openings 23, as shown in Fig. 4, and serve to retain the plunger in the box. The openings are sufficiently large to permit a rcstricted, reciprocating movement of the plunger .in the block. The top surface of the plunger may be knurled as shown at 24 in Fig. 6, or the top of the plunger may be of a non-slip material, such as rubber.

While each block 17 is preferably mounted in the shoulder 16 as described, each of them may be secured on a bracket 25, as shown in Fig. 5, and this bracket fixed to a shaft 26 secured in parallelism with the shaft 12 in the recess 11. Should the brackets 25 be used, the shouldered recess 16 is dispensed with and the shaft with the brackets thereon secured to the platen in any suitable manner.

In operation, after the sheet 14 has been placed in position upon the platen, the iingers 13 are oscillated toward the sheet and caused to press upon the outer side of the sheet along the margin thereof. This action causes depression of the gripper block plungers 18, which are in contact with the under side of t-he sheet in registry with the respective fingers. Since the movement of the plungers is virtually at right angles to the sheet, it is practically impossible to displace the sheet from its adjusted position relative to the aforementioned stops on the tympan. The non-slip surfaces 24 of the gripper block plungers serve to hold the sheet in the desired position for printing thereon, until by the oscillation of the shaft 12 the lingers 13 are released from contact with the sheet, so'that the printed sheet can. be removed from the platen.

f Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A gripper block to be secured to a printing-press platen, having an opening therein; a plunger slidably guided in the opening in the block and having a slot cut through the body thereof; springs in the block beneath the plunger to project the upper side of the plunger above the level of the block; a bar in the block extended through the plunger slot to limit the upward movement of the plunger into contact with the underside of a printing sheet on the platen; and a cooperating element on the platen to press the sheet into contact with the plunger.

2. A gripper block to be secured to a printing press platen, having a rectangular opening therein; a rectangular plunger slidably guided in the opening in the block, having a slot cut through the body thereof; springs in the block beneath the plunger to project the upper side of the plunger above the face of the platen; a barv in the block extended through the slot in the plunger to limit the upward movement of the plunger relative to the face of the platen and to the underside of a printing sheet on the platen; and a cooperating element on the platen to press the sheet into contact with the plunger.

In testimony whereof, I have hereunto set my hand at San Francisco, California, this 27th day of May, 1926.

ROBERT P. KNOX. 

